Controllable pitch propeller and the like



May 24, 1938. N. EG. MEIJER CONTROLLABLE FITCH PROPELLER AND THE LIKE Filed June 14, 1955 y IVN/entor: Nicolaas E. Groeneveld Me Patented May 24, 1938` CONTBOILABLE FITCH PROPELLER AND THELIKE Nicolaas E. Groeneveld Meijer, Schenectady, N. Y., assigner to General Electric Company, a corpora-tion of New York vApplication June 14, 1935, Serial No. 26,603

In Germany January 24, 1935 2 ciaims. (ci. 17o-163) Thisinvention relates to controllable pitch propellers and the like and it has for an object the provision of. a simple, reliable and eflicient propeller of this character,

More particularly the invention relates to controllable pitch propellers in which the force for adjusting the pitch of the blades is produced by thermal energy responsive means, and. a further object is the provision of a controllable pitch propeller in which the elongation of a simple metal body is utilized to adjust the pitch of the blades. Metallic bodies are peculiarly adapted for thermal adjusting elements for large propel- 1ers because of the large forces developed in response to thermal expansion. However, the elongation of a metal rod or sleeve is comparatively small even for a wide range of temperatures, and consequently a body of considerable length is required in order to obtain the necessary amount.

of adjusting motion. Metal bodies of great length, are inconsistent with the limited space of a propeller hub.

In order to eliminate the dimculties which are encountered in arranging a metal body with a suiiicient thermal expansion in the propeller hub, the thermal-adjusting element is formed of a combination of bodies having high and low coefficients of thermal expansion. The individual metal bodies are connected in series in such a way that when heated the bodies with a high coefiicient of thermal expansion have a motion which is opposite to that of the bodies with a low coefficient of thermal expansion. The adjusting elements resulting from this arrangement have 35 a comparatively short length, so that they can be mounted in the propellerf hub without diiiiculty. A particularly advantageous form of the invention results from an arrangement in which the metal bodies with the high and low coei- 4 eients of expansion are designed as sleeves or cylinders alternately telescoped one within another.

This invention constitutes an improvement of the controllable pitch propeller disclosed in ap- 45 plication Serial No. 27,413, iiled June 19, 1935 and assigned to the same assignee.

In illustrating the invention in one form theref of, it is shown as embodied in a thermal energy responsive bimetallic element for adjusting the pitch of the blades of an air craft propeller.

For a better and more complete understanding of the invention, reference should now be had Vto the following specification and to the accompanying drawing in which Fig. 1 is aA sectional view of an embodiment of the invention, Fig. 2

is a fragmentary sectional view illustrating the operation and Fig.3 is a view in elevation illustrating thearrangement of the propeller blades on the hub. l

Referring now to the drawing, a hollow Apro- 5 peller hub I0 is secured to the ilangc ii on the Vend of the motor shaft by suitable fastening means illustrated as bolts I2, i3'.

A pair of propeller blades 8, 9 are mounted in the hub for rotation about their longitudinal lo axes. An adjusting disc Il is secured to the root end of each blade and each disc is provided with an adjustment bolt. As shown, the disc i4 is provided with a bolt I5 and the disc for the opposite blade is provided with a similar adjustl5 ment bolt It.

These bolts are arranged in slots in a yoke member i1 so as to cause the discs and the blades attached thereto, to rotate in opposite directions in response lto straight line movement of the 2 yoke. One end of the yoke is provided with a 0 projection`i1a which slides in a guideway i8, provided in an end plate i9 which is screwed into the hub member i0.

For the purpose of producing the necessary 5 force for rotating the blades about their axes to adjust thel pitch thereof, a thermal energy responsive bimetallic adjustment element 20 is provided which is heated by any suitable means, such for example as the electric heating element 2i. 3@ This heating element is preferably arranged surrounding the bimetallic element, and is supplied with electric power from a suitable external source (not shown) to which it is connected bil means of conductors 22 through slip rings 2t 35 with which stationary brushes make contact. Suitable switching means are, of course, provided for completing and interrupting the connections between the heating element and source to control the pitch adjustment of the blades.

The bimetallic element 20 comprises a plurality of metal bodies, arranged side by side. In the specic form illustrated, a plurality of metal sleeves or cylinders 24, 2S, 26, 21, 28, 28, 30 and 3i of diierent diameters are nested or telescoped one within another. The sleeves 2l, 26, 28 and 3D are preferably made of a metal such as brass having a relatively high coeilicient of thermal expansion whilst the alternate sleeves 25, 21, 2B

. and 3| are preferably made of a metal such as 50 nickel steel having a relatively low coeilicient of thermal expansion. Thus, the sleeves of relatively high and relatively low coeilicient of thermal expansion are alternated with each other. The upper end of the outside sleeve 24 is rigidly 55 connected to the end wall I2 oi the propeller hub i0. The ends of the sleeves 2B, 21, 28 and 3| are connected as by welding or brazing to the ends oi the sleeves 24, 2. 28 and SII in such a manner that one end of a sleeve is connected only with the end ofthe adjacent outside sleeve, while the other end isconnected only with the end oi the adjacent inside sleeve. For example, the lower end of sleeve 24 is connected to the lower end of sleeve 25, and the upper end of the latter is connected to the upper end of sleeve 2i. The sleeves are thus connected in series relationship with each other.

T'he upper end of the inside sleeve is connected with-the rod 33 constituting an extension of 'the yoke iT, the upper end of which slides in a guideway 34 in the end wall 32 of the hub.

When the heating element 2| is connected to the supply source to heat the adjusting element, the external sleeve 24 will elongate (downwardly in the drawing), since the upper end is supported by the solid end wall of the propeller hub. This downward elongation is transmitted by the sleeve 25 to the next sleeve 26, so that the latf ter is also moved downwardly. Since the sleeve 25 is made of metal having a relatively low coefflcient of thermal expansion, it elongates slightly and in the opposite direction, owing to the connection of its lower end with the lower end of sleeve 24. As a result of the heating, the sleeve 2B has also elongated so thatits entire adjusted path corresponds to the sum of the changes in lengths of the sleeves 24 and 26 less the slight change in length in the opposite direction oi sleeve 25. The same applies for the subsequent sleeves 23 and 30 so that the adjusting element, after the heating is completed, will have assumed approximately the position which is shown in Fig. 2. This causes the adjusting yoke to move toward the ange il and thus to cause the discs I4 to rotate and change the pitch o! the propeller blades.

Although in accordance with the provisions oir the patent statutesV this invention is illus-L trated in the best form in which it is now contemplated carrying the invention into effect, it will be understood that the arrangement shown and described is merely illustrative and that the invention is not limited thereto, since alterathemselves to persons skilled in the art'without departing from the true spirit of this inventiony or from the scope of the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. Pitch adjusting mechanism for a controllable pitch propeller having a hollow hub member and a plurality of propeller blades mounted thereon for rotation about their longitudinal axes comprising a plurality of spaced apart concentrically arranged cylindrical bodies having a relatively high coeillcient of thermal expansion and a plurality of cylindrical bodies having a relatively low coeillcient of thermal expansion concentrically arranged in the spaces between said high coefficient bodies, said high and low coeiiicient bodies being connected in series relationship with each other so that the bodies of high and low coecients change their lengths in opposite directions in response to change in temperature, said thermal expansion bodies loeing mounted within said hollow hub, means connecting said thermal expansion bodies to said hub and to said blades, and means for supplying thermal energy to said bodies to produce a force for adjusting the pitch of the blades comprising an electric heating coil within said hub and means for supplying electric power to said coil.

2. Pitch changing mechanism for a controllable pitch propeller having a hollow hub memloer and a plurality of blades mounted thereon comprising means for supplying electric power to the interior of said hub, an electric heating element within said hub for converting electric energy into thermal energy, and a bimetallic element responsive to said thermal energy for produclng a i'orce to adjust the pitch of said blades comprising a plurality or metallic sleeves telescoped one Within another, said cylinders being alternately of metal of relatively high and 10W coemcients of thermal expansion and connected together in series relationship so that said cylinders of high and low coelicients change length in opposite directions and means connecting said himetallic element to said hub and to said blades.

NICOLAAS E. GROENEVELD MEIJER. 

